Composition of matter



Patented Feb. 1,, 1938 UNITED STATES PATENT OFFICE.

1934, Serial No. 743,409.

Divided and this application October 22, 1936, Serial No. 107,016

v 6 Claims. In my copending application Serial No. 743,409,

filed September 10, 1934, I have disclosed a methed for producing new compositions of matter which may take the form of an abrasive powder or of a hard wear-resistingmaterial. The present application is a division of my said copending application and the claims hereof are confined to a hard metal composition as an article of manufacture.

Broadly speaking, the composition of matter constituting the subject matter of the present application takes the form of a carburized or carburized and boronized hard *wear-resisting metallic body made from refractory metal powders alloyed with base metal powder and bon led with a base metal.

This composition of matter is adapted for use as tips for cutting tools, nibs for wire drawing and extrusion dies, sand blast nozzles, contact points, borers for oil well drilling, in fact for practically all types of mechanical and electrical apparatus subject to extreme wear and tear.

The composition of matter of the present invention is non-corrosive and lends itself to use under conditlonswhere prior wear-resisting materials corrode,'tarnish or rust.

My improved material also is of such'a nature as to permit of its use in the arts in place of commercial diamonds.

The starting materials employed in practicing myinvention consist of alloy powders composed of a refractory metal such as tungsten, tantalum, titanium, zirconium, molybdenum, chromium, thorium, rhenium, etc. or other refractory carbide-forming metal having a melting point above 1500 C., and a base metal such as iron, manganese, nickel, cobalt, silver, copper, etc. having a melting point above 1000" C. v

These powders are heat treated with carbon or 40' carbon and boron to produce hard refractory carbides or carbides and borides.

The resulting products are crushed into fine powders and oxides of iron, nickel, cobalt or other base metal added as a' bonding material. The mass is ball-milled to an impalpable powder v which is subjected to low temperature heat treatperature of the final bonding metal, for example, 1400 C., but below the melting temperature thereof. i

I have found that my hard metal composition is far superior to that produced byprior processes. 5

In fact, my hard metal composition is harder, more than twice as tough and stands up more than 25% to as long as a composition produced by mixing the same amounts of base metals with the same amount of tungsten carbide by processes of the prior art. I find also that the structure of the compositions produced by my process, as compared to the structure resulting from mixing tungsten carbide with elementary base metal powder, is very much finer ingrain size and much more compact. Some carbide compositions heretofore have been quite hard, but simultaneously quite brittle. My improved compositions may have a hardness of 88 to 89 on the Rockwell A scale and yet simultaneously be exceedingly tough so that its tensile strength exceeds 300,000 pounds per square inch. 1

More specifically, and assuming that the final product consists of a carburized tungsten, chro mium metal alloy of the iron group bonded with a base metal of the same group, I'may proceed as follows.

It has already been mentioned that my preferred refractory metal is tungsten, although I may use molybdenum, tantalum, titanium, chromium or mixtures of the same, etc. Similarly, it has been mentioned that my preferred'base metal iscobalt, although I may use iron, nickel, cobalt, manganese or mixtures of these.

The first stage or step in the production of my improved material is the alloying stage of producing a mixture of alloy powders of a refractory metal alloyed with metals of the iron group. Accordingly, mixtures in the following proportions are prepared: grams of fine cobalt oxide, 10 grams of chromium and 10 grams of iron oxide are weighed out and mixed, a solution containing 25 grams of thorium nitrates added and the mass slurried into a paste and then dried out. Instead of' the cobalt oxide I may use a precipitated cobalt-tungstate containing 180 grams of cobalt oxide and iron-tungstate containing 10 grams ofiron oxide so that the total contains about 6% to 7% cobalt based on the carbides. These are mixed with tungsten oxide preferably prepared by igniting ammonium paratungstate in proportion of 2350 grams of tungsten oxide to the above mixture.

The first of the above mixtures expressed in terms of the elements is as follows:

Grams Tungsten 1880 Cobalt 142 Chromium l0 Thorium 25 Iron 8 The mixture of dry powders is milled to insure uniform mixture and then placed in nickel boats and treated in an electrically or gas heated furnace through which hydrogen is allowed to flow at about 20 cubic feet per hour, the temperature of the furnace being raised ultimately to from 800 C. to 950 C. By this treatment the powders are reduced and the metals lightly sintered and alloyed together so that they may be removed from the boats, broken up and ground into fine powder. The powder is sieved through a 200 mesh sieve and is now ready for carburizing.

The mixed alloy powders are mixed with lamp black, the quantity of lamp black added depending upon the amount of the refractory carbideforming metal present, the amount of carbon being sufiicient to produce tungsten carbide, chromium carbide and iron carbide in the above example. In the present instance I add 65 grams of carbon (lamp black) per kilo of mixture to be carburized. The mixture is milled and finally placed in carbon tubes closed at both ends. The tubes are placed in a gas furnace in an iron pipe heated to about 950 C. in an atmosphere of hydrogen for two hours. The material is allowed to cool and then removed from the furnace and broken up and again sieved through a 200 mesh sieve. The material is then milled, as before, and subjected to a final carburizing treatment in carbon tubes in suitable electric or gas furnaces at a temperature of about 1250 C. in a carbonaceous, hydrogen or reducing atmosphere.

The resultant product consists of the alloy powders carburized so that the tungsten, iron and chromium have been converted into carbide alloyed with cobalt and this material is powdered to pass through a 300 mesh sieve and mixed with a bonding material such as cobaltic oxide in the proportion of about 1000 grams of the carburized powders to 115 grams of cobalt oxide. This mixture is then milled until reduced to an impalpable powder passing a 350 mesh sieve.

The milled mixture of carburized alloys and cobalt oxide is now placed in nickel boats and reduced in an electric furnace or gas furnaceat about 350 C. in hydrogen gas, this reduction being carried out very slowly at this low tempera.-.

ture so that the resultant productconsists of the carburized alloy powders mixed with cobalt metal powder.

The material is now ready to be shaped into various forms as by pressing in suitable moulds as by mixing with organic binders and extruding the same through various shaped dies, the pressure employed varying over a wide range from, for example, 3 tons per square inch to 30 tons.

The moulded pieces are now baked sumciently to produce adherent bodies and then packed in a carbon boat or tube'surrounded by lamp black and placed in the final heat-treating furnace which is operated at about 1450" C., in any event a temperature below the melting point of the bonding material, although above the plasticizing temperature thereof. The heat treatment is carrled out in a hydrogen or carbonaceoi. atmosphere. The shaped pieces are subjected to this treatment only until the bonding material bearomas Where a combined carburizing and boronizing effect is desired I may add boron suboxide or boron nitride to the originalmixture before al=- loying or just before carburizing. in this case the total carbon and boron in the composition should not exceed 15%.

I find that in the final heat treatment where I employ a temperature of around M50 0., which is below the melting point but above the p1asticizing point of the bonding material, the bonding material is thoroughly absorbed by the alloy powders.

My final hard metal composition may in its final state comprise substantially the following:

Per cent Refractory metals (such as tungsten) 92.5 to 57.5

Iron 0.25to 5.0 Chromium and thorium 0.25 to 2.5 Cobalt and nickel 2.0 to 22.0 Carbon and boron 5.0 to 13.0

More specifically the proportions of materials making up my improved hard wear-resisting metallic body resulting from the above mixture are as follows:

Per cent Tungsten 80. Cobalt 13.0

Carbon 5.0 Thorium 1.15 Iron .4 Chromium .45

If the second alternative is employed, then the mixture will contain only 6% to 7% cobalt.

What I claim is:

1. A hard metal composition consisting of a carburized alloy .comprising tungsten, cobalt, chromium, thorium and iron substantially as follows: tungsten 80% to 90%, cobalt 2% to 13%, chromium and thorium .25% to 2.5%, iron .25% to 1.0%.

2. A hard metal composition consisting of a carburized and boronized alloy comprising tungsten, cobalt, chromium, thorium and iron substantially as follows: tungsten 80% to 90%, co-

balt 2% to 13%, chromium and thorium .25% to 2.5%, iron .25% to 1.0%.

3. A hard metal composition consisting of a carburized alloy comprising tungsten, cobalt, chromium, thorium and iron substantially as follows: tungsten 80% to 90%, cobalt 2% to 13%, chromium and thorium .25% to 2.5%, iron .25% to 1.0%, said composition having a hardness above 89 on the Rockwell A scale and simultaneously a-tensile strength exceeding 300,000 pounds per square inch.

4. A hard metal composition consisting of a carburized and boronized alloy comprising tungsten, cobalt, chromium, thorium and iron substantially as follows: tungsten to cobalt 76 sisting of a carburized alloy comprising tung- 2%to 13%, chromium and thorium .25% to 2.5%, iron .25% to 1.0%, said composition having a hardness above 89 on the Rockwell A scale and simultaneously a tensile strength exceeding 300,000 pounds per square inch.

5. A wrought hard metal composition consten, cobalt, chromium, thorium and iron substantially. as follows: tungsten 80% to 90%,

cobalt 2% to 13%, chromium andv thorium .25% to 2.5%, iron".25% to 1.0%, said composition having a hardness above 89 on the Rockwell A scale and simultaneously a tensile strength ex-'- seeding 300,000 pounds per square inch.

6. A wrought hard metal composition consisting of a. carburized and boronized alloy comprising tungsten, cobalt, chromium, thorium and iron substantially as follows: tungsten 80% to 90%, cobalt 2% to 13%, chromium and thorium 25% to 2.5%, iron 25% to 1.0%, said composition having a hardness above 89 on the Rockwell A" scale and simultaneously a tensile strength ex- 10 ceeding 300,000 pounds per square inch.

C on. 1N8 A. LAISE. 

